$A$ train completes a non-stop journey in $8 \, \text{hours}$. If it had travelled $5 \, \text{km/h}$ faster, it would have completed the journey in $6 \, \text{hours} \, 40 \, \text{minutes}$. What is its lowest speed in $\text{km/h}$?

How many seconds will a $500 \, m$ long train take to cross a man walking with a speed of $3 \, km/h$ in the direction of the moving train, if the speed of the train is $63 \, km/h$?

Ravi and Ajay start simultaneously from a place $A$ towards $B$,$60 \, km$ apart. Ravi's speed is $4 \, km/h$ less than that of Ajay. Ajay,after reaching $B$,turns back and meets Ravi at a place $12 \, km$ away from $B$. Ravi's speed is (in $km/h$):

$A$ car travels from $P$ to $Q$ at a constant speed. If its speed were increased by $10 \, km/h$,it would have taken $1 \, hour$ less to cover the distance. It would have taken a further $45 \, minutes$ less if the speed was increased by another $10 \, km/h$. The distance between the two cities is (in $km$):

$A$ person has to reach a certain place at a certain time. He finds that he will be $15 \text{ minutes}$ late if he walks at $4 \text{ km/h}$,and $10 \text{ minutes}$ earlier if he walks at $6 \text{ km/h}$. How far has he to walk? (in $\text{km}$)

Two trains are running in opposite directions with speeds of $62 \, km/h$ and $40 \, km/h$,respectively. If the length of one train is $250 \, m$ and they cross each other in $18 \, seconds$,then the length of the other train is (in $m$):